Obafemi Martins' agent has insisted the player has missed Nigeria's recent games because of injury.
Reports in Nigeria suggested Martins had clashed with management, but it is now claimed the player has an ankle problem.
Indeed it is now believed Martins could miss the start of the Premier League season.
"First of all, I would like to say that Obafemi takes his country's assignments very seriously. He is very patriotic and is proud to be Nigerian," Chris Nathaniel told Nigerian newspaper Kick-Off.
"He actually had ankle injuries which he managed to play the last matches of his club season with the aid of pain killers.
"In order not to aggravate the injuries, he had to see a doctor on time and right now he is in Italy for a check-up to determine the extent of the ankle injuries.
"Obafemi and I made attempts to inform the NFA officially, despite the fact that his injuries have been widely reported in newspapers.
"Nigeria coach Shaibu Amodu did not communicate with the player and he also found it difficult to get across to the coach before the Austria friendly. They do not have his contact addresses, telephones, e-mails and the rest. Martins should not be blamed for Amodu's inability to get his correct contact details.
"I think it is the duty of the staff of the NFA to make sure they have the details of all the players playing for the nation. And if they had done that, then the coach would be able to get in contact with Obafemi without any problem. I don't think anybody can blame the player for that."
Amodu admitted that Martins was injured and even suggested he could be out for up to nine weeks.
"Obafemi did not turn up because of an ankle injury, the doctors said to him he could be out for up to nine weeks."
It now remains to be seen whether Martins will be fit to return for pre-season training with Newcastle.